Techniques for tightening a target to be tightened with a fastener (a fastener component) such as a bolt or rivet are used for assembling an airplane or the like. A rivet driving device for tightening the target to be tightened with the rivet is known.
An automatic rivet driving device disclosed in a patent literature 1 (JP 2000-135541A) includes a riveter body that has a mechanism for driving the rivet into a work. The riveter body has a C-shape, which sandwiches the work in upper and lower direction. An upper head portion is provided at a top tip of the riveter body. A die is placed at a bottom tip of the riveter body.
FIG. 1 shows the above mentioned upper head portion 351. The upper head portion 351 is capable of reciprocating in the arrow direction by an oil hydraulic cylinder 352. On a bottom surface of the upper head portion 351, namely, on a position facing to a top surface side of a work 304, an elevating drill spindle 353, an elevating rivet swaging tool 354, and an elevating shaving cutter 355 are arranged on a straight line parallel to the arrow direction. A drill 356 is attached to the drill spindle 353. After the work 304 is set, the drill spindle 353 is lifted down and a rivet hole 304a is formed in the work 304. Next, the oil hydraulic cylinder 352 moves the rivet swaging tool 354 to a position at which the drill spindle 352 has been located. Next, the rivet swaging tool 354 descends with holding a rivet R to insert a shaft portion of the rivet R into the rivet hole 304a. Moreover, the rivet R is pushed by the die placed at the bottom tip of the riveter body and the rivet swaging tool 354. Thus, driving of the rivet R is completed. Meanwhile, the shaving cutter 355 is used when a head of the rivet R is removed.
A patent literature 2 (JP 2002-28745A) and a patent literature 3 (JP Heisei-5-000242U) disclose other rivet driving devices.
In recent years, cases are increasing in which a composite material component such as fiber-reinforced plastic is used instead of a metallic component. For example, many composite material components have been used in an airplane.
With reference to FIGS. 2 to 7, a method of manually tightening the target to be tightened which is a composite material will be explained.
With reference to FIG. 2, a work 100 that is the target to be tightened includes a plurality of piled composite material components 51 and 52. A countersunk hole 100a is provided, penetrating from a surface 100b of one side of the work 100 to a surface 100c of the other side. A countersunk portion of the countersunk hole 100a is arranged on the surface 100b side. The work 100 has a countersunk hole wall surface 100d that surrounds the countersunk portion of the countersunk hole 100a. After the formation of the countersunk hole 100a, the work 100 is cleaned, and burrs formed during the formation of the countersunk hole 100a are removed.
FIG. 3 shows a fastener 25 which is the fastening component for tightening the work 100. The fastener 25 includes a countersunk bolt 20 and a sleeve 40. The countersunk bolt 20 includes a head portion 21, a cylinder portion 22 and a screw portion 23. The head portion 21 includes a head top surface 21a and a head side surface 21b. The head side surface 21b is a conic surface. The cylinder portion 22 is arranged between the head portion 21 and the screw portion 23. A screw is not formed in the cylinder portion 22. The screw portion 23 has an end surface 23a. The head top surface 21a and the end surface 23a are arranged at both ends in an axis direction of the fastener 25. The sleeve 40 covers the cylinder portion 22. The cylinder portion 22 is exposed from the sleeve 40 at a portion close to the head portion 21. The sleeve 40 includes a countersunk portion 41 arranged on the head portion 21 side, and a cylinder portion 42 arranged on the screw portion 23 side. The countersunk portion 41 is cone-shaped.
With reference to FIG. 4, the fastener 25 is pushed into the countersunk hole 100a so that the countersunk portion 41 contacts with the countersunk hole wall surface 100d. When the countersunk portion 41 contacts with the countersunk hole wall surface 100d, the head portion 21 is protruded from the surface 100b, and the screw portion 23 is protruded from the surface 100c. 
With reference to FIG. 5, impact forces are repeatedly added to the head top surface 21a by an air hammer 200 to drive the fastener 25.
With reference to FIG. 6, until the fastener 25 is seated on the work 100, namely, until the head portion 21 contacts with the countersunk hole wall surface 100d through the countersunk portion 41, the impact forces are repeatedly applied to the head top surface 21a by the air hammer 200. Here, a worker determines, by a tone, that the fastener 25 is seated, and stops the addition of the impact forces by the air hammer 200.
With reference to FIG. 7, a nut 30 is attached to the screw portion 23, and the composite material components 51 and 52 are tightened.
Here, since the impact forces are repeatedly applied to drive the fastener 25, a risk of damages in the composite material components 51 and 52 is reduced, compared with a case where the fastener 25 is pushed until the head portion 21 contacts with the countersunk hole wall surface 100d through the countersunk portion 41. However, in a case where a process for repeatedly applying the impact forces to drive the fastener 25 is automated, some kind of means is necessary for automatically detecting the seating of the fastener 25.
Also, in a case where the automatic rivet driving device disclosed in Patent literature 1 (JP 2000-135541A) is used for driving the rivet into the composite material, following problems may be arisen. When the above mentioned work 304 is the composite material, after the formation of the rivet hole 304a, the work 304 is removed from the automatic rivet driving device and the burrs formed during the formation of the rivet hole 304a are removed. After that, the work 304 is set again in the automatic rivet driving device, and the rivet swaging tool 354 is lifted down for inserting the shaft portion of the rivet R into the rivet hole 304a. Here, since the work 304 is set again, a misalignment may be occurred between the rivet swaging tool 354 and the rivet hole 304a. 